[PATCH] Fix assert failure in invocation of "[kill|detach] inferiors 1"

[Patrick Palka <patrick@parcs.ath.cx>]

When only the dummy PID 0 inferior exists, invoking either of the above
commands triggers the following assert failure:

  .../binutils-gdb/gdb/thread.c:514: internal-error: any_thread_of_process: Assertion `pid != 0' failed.

The fix is straightforward.  Tested on x86_64 Debian Stretch.

gdb/ChangeLog:

	* inferior.c (detach_inferior_command): Don't call
	any_thread_of_process when pid is 0.
	(kill_inferior_command): Likewise.

gdb/testsuite/ChangeLog:

	* gdb.base/no-inferiors.exp: New test file.
---
 gdb/inferior.c                          | 12 ++++++++++--
 gdb/testsuite/gdb.base/no-inferiors.exp | 24 ++++++++++++++++++++++++
 2 files changed, 34 insertions(+), 2 deletions(-)
 create mode 100644 gdb/testsuite/gdb.base/no-inferiors.exp

diff --git a/gdb/inferior.c b/gdb/inferior.c
index 5e98df5..ff85a1f 100644
--- a/gdb/inferior.c
+++ b/gdb/inferior.c
@@ -626,7 +626,11 @@ detach_inferior_command (char *args, int from_tty)
 
       pid = gdb_inferior_id_to_pid (num);
 
-      tp = any_thread_of_process (pid);
+      if (pid != 0)
+	tp = any_thread_of_process (pid);
+      else
+	tp = 0;
+
       if (!tp)
 	{
 	  warning (_("Inferior ID %d has no threads."), num);
@@ -662,7 +666,11 @@ kill_inferior_command (char *args, int from_tty)
 
       pid = gdb_inferior_id_to_pid (num);
 
-      tp = any_thread_of_process (pid);
+      if (pid != 0)
+	tp = any_thread_of_process (pid);
+      else
+	tp = 0;
+
       if (!tp)
 	{
 	  warning (_("Inferior ID %d has no threads."), num);
diff --git a/gdb/testsuite/gdb.base/no-inferiors.exp b/gdb/testsuite/gdb.base/no-inferiors.exp
new file mode 100644
index 0000000..2ccf4ce
--- /dev/null
+++ b/gdb/testsuite/gdb.base/no-inferiors.exp
@@ -0,0 +1,24 @@
+# This testcase is part of GDB, the GNU debugger.
+#
+# Copyright 2015 Free Software Foundation, Inc.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+# Check that invoking various commands that take an inferior ID does not cause
+# an internal error when only the dummy inferior with PID 0 exists.
+
+gdb_start
+
+gdb_test "detach inferiors 1" "warning: Inferior ID 1 has no threads."
+gdb_test "kill inferiors 1" "warning: Inferior ID 1 has no threads."
-- 
2.5.0.rc2.22.g69b1679.dirty